The present invention relates to a method for fabricating active elements for a laser source.
It is known that a laser source generally comprises at least:
an at least partially doped active element, in which a stimulated amplification (laser) phenomenon is generated;
a pumping system generating a pump beam which is emitted in said active element so as to provide the energy needed for said laser amplification; and
an optical cavity which endows the laser beam obtained by this amplification with its directivity and geometrical characteristics.
More particularly, the present invention relates to the fabrication of active elements comprising at least one doped part comprising an absorbent doping capable of absorbing a pump beam in order to amplify laser radiation and at least one undoped part, not comprising such an absorbent doping.
Within the scope of the present invention, the term xe2x80x9cundopedxe2x80x9d part or block refers to a part or a block not comprising said absorbent doping, that is to say a part or a block which does not absorb the pump (pump beam). Nevertheless, this part and this block may include a particular doping intended for a purpose other than absorbing the pump.
In order to fabricate an active element of this sort, the following operations are generally carried out in succession:
a) the element forming the undoped part is cut and polished;
b) the element forming the doped part is cut and polished;
c) these two elements are joined so as to form an active element; and
d) the surfaces of this active element are treated.
Of course, when it is desired to fabricate a plurality of such active elements, it is necessary to carry out the aforementioned sequence of operations a) to d), individually, for each of these active elements.
Consequently, the fabrication of a plurality of identical active elements is lengthy and expensive.
The object of the present invention is to overcome these drawbacks. It relates to a method for fabricating, quickly, efficiently and at reduced cost, active elements for a laser source.
According to the invention, said method for fabricating active elements for a laser source, each of said active elements comprising at least one doped part comprising an absorbent doping capable of absorbing a pump beam in order to amplify laser radiation and at least one undoped part, not comprising such an absorbent doping, each of said active elements having a first face and a second opposed face each of which has the same geometrical shape and which are separated one from the other by a predefined distance, is noteworthy in that the following is carried out in succession:
A) a process of preparing an elongate active rod, which has a cross section identical to said geometrical shape and a length at least twice the size of said predefined distance between the first and second faces of an active element, said preparation process comprising at least one cutting step and a step of joining at least one doped elongate block comprising said absorbing doping and at least one undoped elongate block not comprising said absorbent doping; and
B) a process of forming a plurality of active elements from said active rod, said formation process comprising at least one step of transversely cutting along said active rod and a step of collectively treating surfaces of said active elements.
Thus, by virtue of the invention for fabricating active elements, a semifinished product (the active rod) is produced, which makes it possible to carry out collectively, that is to say for all the active elements to be fabricated, at least:
the joining [of the doped and undoped block(s)], during the rod preparation process; and
the treatment of surfaces, during the process of forming active elements.
Consequently, the active elements can be fabricated quickly and at reduced cost, since, instead of carrying out a plurality of individual operations for each of the joining and surface treatment steps, only a single simple collective operation is carried out.
In a first embodiment, during said formation process, the following is carried out in succession:
a) said step of collectively treating surfaces, consisting in treating the surfaces of said active rod; and
b) said transverse cutting step consisting in cutting said active rod treated in this way so as to form a plurality of active elements comprising said first and second faces separated one from the other by said predefined distance.
Furthermore, in a second embodiment, during said formation process, the following is carried out in succession:
a) said transverse cutting step consists in cutting said active rod so as to form a plurality of active elements comprising said first and second faces separated one from the other by said predefined distance; and
b) said step of collectively treating surfaces, wherein at least some of the active elements formed in this way are reassembled by simply bringing the first and second faces into contact so as to obtain an at least partially reconstructed active rod and the surfaces thereof are treated, that is to say the surfaces of said reassembled active elements are treated collectively.
Preferably, during said formation process, the cut faces corresponding to said first and second faces of the active elements are polished, after the transverse cutting step. However, if the cutting step is accurate enough, it is possible that the cut faces may not have to be polished.
In addition, at said cutting step:
in a first variant, transverse cuts are carried out successively by means of the same diamond saw; and
in a second variant, a plurality of transverse cuts are carried out simultaneously by means of a saw comprising a comb of parallel blades, which makes it possible to reduce the cutting time and therefore the implementation time of the fabrication method according to the invention.
Moreover, during said process of preparing the active rod, in a first variant, the following are carried out in succession:
a) said cutting step, consisting in cutting said elongate blocks [doped and undoped] to sizes such that, when they are joined one to the other, they form said active rod having a cross section identical to said geometrical shape and a length which is at least twice said predefined distance between the first and second faces of an active element; and
b) said joining step consisting in joining said elongate blocks so as to form said active rod.
Furthermore, in a second variant, the following are carried out in succession:
a) said joining step consisting in joining said elongate blocks so as to form an active unit; and
b) said cutting step, consisting in cutting said active unit so as to obtain said active rod having the desired dimensions, that is to say a cross section identical to said geometric shape and a length which is at least twice said predefined distance between the first and second faces of an active element.
Moreover, according to the invention, during or before said preparation process, or after the formation of the active rod, the faces of said elongate blocks, which are visible when said elongate blocks are in a position corresponding to the joining position, are polished.
Although, within the context of the present invention, the blocks may be joined one to the other by means of various known techniques, such as adhesive bonding for example, this joining is preferably carried out by means of welding of the normal type.
In a particular embodiment, said active rod is formed from one doped elongate block and from two undoped elongate blocks. In this case, preferably, said doped elongate block has the shape of a plate and said two undoped elongate blocks are identical and are attached on either side of said plate.